Dynamic compressive behavior of impact-damaged and water-soaked sandstone with different length-to-diameter ratios.

In backfill mining, surrounding rock damaged by impact loading (e.g. blasting) is immersed in backfill water after backfilling, and the instability of the impact-damaged and water-soaked (IDWS) surrounding rock can occur under blasting loads. To study the dynamic mechanical properties and the size effect of rock under such working conditions, triaxial dynamic compression tests were conducted on four groups (four length-to-diameter ratios) of first impact-damaged and then water-soaked sandstone specimens using an improved split Hopkinson pressure bar device. The test results show that, at a similar strain rate (approximately 10 s−1), the peak strength and elastic modulus of IDWS specimens are lower than those of the intact specimens, whereas the peak strain is higher than that of the intact specimens. Both the peak strength and peak strain of the IDWS specimens increase with strain rate, exhibiting a strong strain rate dependency. The peak strength, peak strain, and elastic modulus all display a size effect. This size effect varies over different strain rate ranges. When the strain rate is approximately 10 s−1, the peak strength decreases as the length-to-diameter ratio increases. In contrast, at a strain rate of approximately 30 s−1, the peak strength increases with an increase in the length-to-diameter ratio. There is a linear relationship between the incident energy and absorbed energy of the intact and IDWS specimens. Under the same incident energy, the IDWS specimens show higher absorbed energy than the intact specimens. This relationship is independent of the length-to-diameter ratio of rock specimens. [ABSTRACT FROM AUTHOR]